SURVEY OF INVERTEBRATES 57 



sphaerica. Most of his experiments were performed with 

 Trichomonas termopsidis and he could show that this 

 organism develops very well even in the complete ab- 

 sence of oxygen. But, curiously enough, Gilmour (1940) 

 observed that the termite parasites were harmed when 

 their hosts were exposed to nitrogen. The population of 

 TricJionympha, in particular, decreased after 5 hours or 

 more. This may, he thinks, be readily explained by as- 

 suming an accumulation of abnormal endproducts of the 

 anaerobic metabolism of the host, causing injury to the 

 parasites. The experiences gathered so far seem, on the 

 whole, to give credence to the idea that the termite intes- 

 tinal parasites have but little, if any oxygen available in 

 their normal habitat. 



Many hlood parasites of vertebrates undergo part of 

 their life cycle in the intestine of invertebrates. The first 

 stage of development in this habitat is in many cases the 

 formation of gametes from gametocytes. Marchoux and 

 Chorine (1932) have shown that the formation of both 

 macro- and microgametes of Haemoprotcus colwnbae is 

 possible in an atmosphere of hydrogen. 



Since, in culture, blood parasites usually assume the 

 forms characteristic of the stages present in the intestine 

 of the intermediate host rather than the form found in 

 the blood stream of the definitive host, we shall discuss 

 in this section their behavior as observed in culture. It 

 has been shown that the developmental stages of Trypan- 

 osomidae are fairly resistant to lack of oxygen but no 

 unanimity of opinion on this point exists among the dif- 

 ferent investigators. Soule (1925), Adler and Theodor 

 (1931) and Ray (1932) reported that Trypanosoma 

 lewisi and various Lcishmania species, in cultures, with- 

 stand anaerobic conditions for periods up to 8 to 14 

 days, but that they do not multiply. Senekji (1941), on 

 the contrary, found a good growth under anaerobic con- 

 ditions in cultures of five Lcishmania species. In view of 

 these contradictory results it is impossible, at the pres- 



